Method useful for rotational molding articles where successful runs are of different colors

ABSTRACT

A method wherein an article is molded of a heat-fusing material or plastisol in a mold having first and second groups of liquid passages disposed adjacent the mold surface for controlling the temperature over respective first and second areas of the mold surface. The mold is supported for rotation about an axis by a stationary pedestal. A movable module supports plastisol storage tanks, heat exchangers, valves, conduits, etc., for supplying the plastisol to the mold. The movable module also supports a dump tank which is disposed beneath the mold for receiving and retrieving the liquid plastisol which is emptied or dumped from the mold when it is rotated to an inverted position. There is included first and second liquid circuits including a pump and heat exchanger for supplying liquid at different temperatures to the passages associated with the mold. All of the passages are supplied with heated liquid to maintain the temperature of the first and second areas of the mold surface at a non-gelling temperature and a liquid plastisol coating is applied to the mold surface. To obtain the coating, the mold is filled and the excess plastisol is removed from the mold by dumping the plastisol from the mold into the dump tank as the mold is rotated to leave the coating.

RELATED APPLICATION

This application is a division of application Ser. No. 832,640 filedSept. 12, 1977, now U.S. Pat. No. 4,217,325, which is, in turn, acontinuation-in-part of U.S. application Ser. No. 789,410, filed Apr.21, 1977, now abandoned.

BACKGROUND OF INVENTION

(1) Field of Invention

This invention relates to a method and an assembly for practicing themethod of molding hollow thin-walled articles from a heat-fusingmaterial such as vinyl plastisol by slush molding.

Various vinyl plastisol compositions are known and used in various slushmolding methods in various assemblies for performing those methods.Typically, an open hollow mold is filled with liquid plastisol and heatis applied to the mold surface and transferred to the liquid plastisolto gell a layer of plastisol adjacent the mold surface. The thickness ofthe gelled layer depends upon the temperature to which the plastisollayer is subjected and the time the plastisol is maintained at thattemperature. After the layer adjacent the mold surface is gelled, theungelled liquid plastisol remaining is dumped or poured out of the mold.

(2) Description of the Prior Art

In one well-known method, the mold temperature is maintained relativelylow to prevent gelling as a very thin initial layer or coating ofplastisol is applied to the mold to prevent bare spots and to preventthe entrapment of air bubbles, thereby providing a thin coating whichstrictly conforms to the mold configuration. Such a coating is appliedby filling and emptying the mold. For example, automotive dashboard orinstrument panel covers are made in this fashion and the moldsfrequently include details to define imitation stitching in the finishedproduct as well as undercuts and other intricate detail. The very thincoating is first applied to conform to the mold and to preventirregularities in the outer surface of the finished product. After thisvery thin coating is applied, the mold is again filled with additionalplastisol and the entire mold is heated to gel the plastisol andincrease the thickness of the finished product. After the desiredthickness is attained, the mold is again dumped or emptied andthereafter the mold is subjected to additional heat for curing theproduct.

An example of such a method and an assembly for practicing same is shownin the U.S. Pat. No. 3,728,429 granted to Daniel E. Colby, Philip E.Rogers and Frederick J. Sliwinski on Apr. 17, 1973 and assigned to theassignee of the subject invention. That patent discloses such a methodfor slush molding articles wherein the mold is heated by the exteriorsurfaces thereof being exposed to impinging streams of hot gas and,after the product is finished, the mold is cooled by being subjected tocooling water from water spray nozzles, after which the fused finishedarticle is stripped from the mold. In addition, an endless conveyormoves a plurality of molds through various stations in the performanceof the method. Although the method and assembly shown in this patenthave proven to be very satisfactory, there are disadvantages such as theopen flame adjacent the molds, which produces the hot gas for heating ofthe molds, and the use of water or liquid for cooling the molds andwhich can be incompatible with the plastisol. Further, the assembly,because of its long conveyor and multiple molds, is suited for long runsof a plastisol of a particular color but is not well suited for shortruns or quick or efficient changeovers.

Other methods of heating in a slush molding process have been utilizedin the prior art; for example, the molds may be moved through heatingovens as exemplified in U.S. Pat. No. 3,002,230 granted to J. W. Stewarton Oct. 3, 1961. Alternatively, the molds may be subjected to inductionheaters as exemplified in U.S. Pat. No. 3,315,016 granted to John M.Wersosky and Donald A. Moore on Apr. 18, 1967 and assigned to theassignee of the subject invention. Another method for heating the moldis exemplified in U.S. Pat. No. 3,680,629 granted to Laurent R. Gaudreauand Floyd E. McDowell on Aug. 1, 1972 and assigned to the assignee ofthe subject invention. That patent teaches the heating of a mold byincorporating tubes in the mold and flowing a heated fluid such as steamthrough the tubes for heating the mold. It is also known in the slushmolding art to heat the mold by such tubes for conveying liquid throughthe mold wherein there are multiple circuits of the tubes with eachcircuit having an inlet and an outlet, but with each circuit subjectedto the same fluid medium, i.e., the same temperature.

One of the problems associated with the prior art methods is that inmany articles which are manufactured by slush molding where the mold isfilled with plastisol, some areas of the filled mold are at a lowerliquid level of the plastisol and are salvage or trim areas which arenot used in the final product and therefore do not require the thicknessof the other finished areas in the product. Yet, when the entire moldsurface is heated uniformly the entire finished article hasapproximately the same thickness even though some areas are trim ornon-usable. There is known in the slush molding art the technique ofvarying the thickness by heating different areas of the mold to a higherdegree to increase the thickness of the article in certain areas. Such atechnique is exemplified in U.S. Pat. No. 2,588,571 granted to SydneyPorter on Mar. 11, 1952. That patent discloses the technique of slushmolding a boot by utilization of infrared lamp heating and shielding theheating from certain portions of the mold to prevent the build-up of theplastisol thickness and to increase the thickness of the sole of theboot by increased heating.

SUMMARY OF THE INVENTION

The subject invention provides an improved method and assembly forperforming the method of controlling the thickness of an article made bythe slush molding process in a mold having first and second groups ofliquid passages disposed adjacent the mold surface for controlling thetemperature over respective first and second areas of the mold surface.The first group of liquid passages are disposed adjacent the first areaof the mold surface where it is desired to increase the thickness of thefinished article whereas the second group of passages are disposedadjacent the second area of the mold surface where the material in thefinished article is scrapped and/or will be trimmed and therefore thedesired thickness is desirably less. Both the first and second groups ofpassages are supplied with liquid to maintain the temperature of thefirst and second areas of the mold surface at a non-gelling temperatureas liquid plastisol is disposed over the mold surface to define acoating or layer. This very thin coating of plastisol is applied to befree of surface blemishes. Thereafter, additional liquid plastisol isprovided for increasing the thickness only over the first area of themold surface. To accomplish this, the first group of passages issupplied with a liquid at a temperature higher than the non-gellingtemperature of the liquid in the second group of passages for heatingthe first area of the mold surface to a higher temperature than thesecond area so as to gel the liquid plastisol over the first area of themold surface which is heated with the heat supplied by the liquid in thefirst group of passages. After the desired gelled thickness is attained,all passages are supplied with liquid at a temperature sufficient toheat the first and second areas of the mold to a cure temperature forcuring all of the plastisol. Accordingly, the finished article will havea greater thickness over the first area which defines the finished areaof the article whereas the thickness of the article over the second areaof the mold surface will be much thinner and define the scrap or trimareas. Consequently, significant amounts of material are saved.

Another aspect of the subject invention is the provision of an assemblyfor a slush molding which includes a stationary pedestal rotatablysupporting a mold support means for rotation about an axis for rotatinga mold supported thereby to empty the mold of liquid plastisol and amovable module for supplying liquid plastisol to the mold supported bythe mold support means with a dump tank movable therewith and disposedunder the mold support means when the module is in the operatingposition relative to the pedestal for receiving plastisol emptied fromthe mold. Accordingly, one such module may be utilized for supplying aspecific plastisol for a given number of articles made by a moldsupported on the pedestal and to change plastisols very rapidly andquickly for continuing the run. It is only necessary to substituteanother module having another plastisol as, for instance, a plastisol ofa different color.

PRIOR ART STATEMENT

The U.S. Pat. No. 3,728,429 discussed above discloses a slush moldingprocess wherein the mold is heated by being subjected to hot gases andcooled by being subjected to cooling water and wherein the molds move onan endless conveyor through various stations. There is no suggestion inthat patent of the subject inventive concept of utilizing first andsecond groups of passages for differential heating of the mold forcontrolling the thickness of the article formed therein. Furthermore,there is no suggestion of utilizing a modular system as suggested by thesubject invention wherein a particular module may be moved into positionrelative to the mold for making a first plurality of articles of onecolor and thereafter another module may be moved in position relative tothe mold for making a plurality of the same articles but of a differentcolor. The above-mentioned U.S. Pat. No. 3,680,629 suggests the use ofliquid passages adjacent the mold surface for controlling thetemperature of the mold, however, there is no suggestion in that patentof using first and second groups of passages and control means forsupplying liquids at different temperatures to the first and secondgroups of passages respectively. Even though there may be known in theprior art molds with two separate groups of passages adjacent the moldsurface, there is no suggestion of utilizing control means for supplyingliquid at different temperatures in different sequences to therespective groups of passages for differentially heating the moldsurface. As alluded to above in regard to U.S. Pat. No. 2,588,571, thetechnique of varying the thickness by differential heating is known inthe slush molding art, however, such is accomplished by infraredheating. There has been no recognition in the prior art of theadvantages of differentially heating and cooling the surfaces of themold used in the slush molding process by utilizing different groups ofliquid passages adjacent the mold surface and a control means forsequentially supplying those passages with liquids at differenttemperatures. Further, there has been no recognition in the prior art ofthe advantages of utilizing a modular approach to the slush moldingprocess wherein one module may be utilized with a mold for a given runof articles of one color and a second module thereafter utilized withthe same mold for making a plurality of articles of a different color.

BRIEF DESCRIPTION OF DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a perspective view of a preferred embodiment of an assemblyconstructed in accordance with the subject invention;

FIG. 2 is a fragmentary cross-sectional view showing a mold supported ina mold support means for utilization with the subject invention;

FIG. 3 is a schematic view of the liquid circuits utilized to heat andcool a mold in accordance with the subject invention; and

FIG. 4 is a schematic view showing a plastisol supply and retrievalcircuit utilized with the subject invention.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 shows an assembly generally indicated at 10 and constructed inaccordance with the subject invention. The assembly 10 includes astationary pedestal generally indicated at 12 for rotatably supporting amold support means generally indicated at 14. The pedestal 12 rotatablysupports the mold support means for rotation about the axis A--A. Themold support means 14 is a box or coffin-like structure which receivesand supports a mold 16. The mold 16 has a mold cavity defining a moldsurface.

The pedestal 12 is stationary and includes a base 18 and spaced supportlegs 20. The support legs 20 rotatably support the mold support means 14through large circular bearings (not shown) disposed on collars orsleeves 22, which collars or sleeves 22 have accesses or openingsthrough the center thereof, the purpose of which will be explainedhereinafter. The mold support means 14 is rotated through a large chainsprocket disposed within the housing 24 and secured to the sleeve 22. Achain is entrained about the large sprocket and is entrained about adrive sprocket rotated by a motor supported upon the base 18.

The assembly 10 also includes a movable modular unit generally shown at26 for supplying liquid heat-fusing material such as a plastisol to theopen mold 16. The entire unit 26 is supported on a plurality of rollers28 and includes a dump tank 30. The dump tank 30 is movable with theentire unit 26 and is normally disposed under the mold support means 14when the unit 26 is in the operating position illustrated in FIG. 1relative to the pedestal 12 for receiving plastisol emptied from themold 16 as the mold 16 is rotated for dumping or emptying into the dumptank 30. As alluded to above, the mold 16 may be supplied with adifferent plastisol or the same plastisol of a different color merely bymoving the modular unit 26 away from the mold and inserting or placing adifferent modular unit in position having a different plastisol.Further, and as will become clear hereinafter, the preferred embodimentof the unit 26 includes two modules for supplying two differentplastisols whereby two different plastisols may be sequentially suppliedto the mold. This can result in a continuous production cycle utilizinga particular mold 16 to make the same product or article of differentcolors.

The modular unit 26 is a plastisol supply and retrieval module forsupplying liquid plastisol to the mold surface of the mold 16 and forretrieving liquid plastisol emptied or dumped from the mold 16. Therollers 28 define a conveyance means for fascilitating the movement ofthe unit 26 away from the pedestal 12 and the mold support means 14.

The mold 16 has a molding surface on the interior thereof which must beheated for the plastisol to gel. A first group of liquid passages 32 aredisposed adjacent the mold surface over a first area 34 of the moldsurface for controlling the temperature over the first area 34 of themold surface. Additionally, a second group of liquid passages 36 aredisposed adjacent the mold surface over a second area 38 of the moldsurface for controlling the temperature over the second area 38.

A first manifold means, including a pair of manifolds 40 are supportedby the mold support means for distributing liquid to and collectincliquid from the first group of passages 32. More specifically, amanifold 40 is disposed at each end of the mold support means 14 and therespective fluid passages or conduits 32 extend between the twomanifolds 40. Each conduit 32 is connected to the manifold through aregulating valve 42 having a manual adjustment 44 whereby the liquidflow in each respective line 32 may be manually adjusted. In a similarfashion, the assembly includes a second manifold means comprising a pairof manifolds 46 disposed at the respective ends of the mold supportmeans 14 for distributing liquid to and collecting liquid from thesecond group of passages 36. Further, each passage 36 is connected tothe manifold 46 through a regulating valve 42 having a manual adjustment44. It will be appreciated that the regulating valves 42 need only bedisposed at one end of the mold support means 14 for regulating thefluid flow through the respective passages 32 and 36.

As used herein, the term first group of liquid passages and/or the termsecond group of liquid passages may include any number of passagesincluding one singular passage. Further, the terminology that thepassages are disposed adjacent the mold surface is intended to coverembodiments where the tubes defining the passages 32 and 36 are welded,braised or otherwise attached to the surfaces of the mold, asillustrated, or partially or completely embedded in the walls of themold section. Additionally, the groups of passages may be defined otherthan by the tubes illustrated so long as the passages are defined tosupply liquid at different temperatures to differentially heat the areasof the mold and to retrieve the liquid for recirculation, i.e., a closedsystem for the liquid.

The first supply line 48 is in communication with the manifolds 40 ofthe first manifold means and a second supply line 50 is in communicationwith the manifolds 46 of the second manifold means. As alluded to above,the rotatable supports or sleeves for the mold support means 14 on thelegs 20 have circular openings therethrough at each end and the lines 48and 50 extend therethrough, as illustrated in FIG. 1. A first swivelmeans or joint 52 is associated with each end of the line 48 and isdisposed on the axis A--A for allowing the first supply line 48 torotate with the mold support means 14. In a similar fashion, the lines50 extend through two 90° elbows to a second set of swivels 54 defininga second swivel means disposed on the axis A--A in axially spacedrelationship to the swivels 52 for allowing both ends of the secondsupply line 50 to rotate with the mold support means 14. As will beappreciated from viewing FIG. 1, the supply line 50 moves about the axisof the supply line 48 and, therefore, the degree of rotation of the moldsupport means 14 is limited to approximately 270°.

There is also included a control means generally shown at 54 in FIG. 3for sequentially supplying liquid to the first and second groups ofpassages 32 and 36 for maintaining the temperature of the first andsecond areas 34 and 38 of the mold surface at a non-gelling temperaturebelow that required to gel any appreciable thickness of the plastisolover the mold surface and for thereafter heating the first area 34 ofthe mold surface to a higher temperature than the second area 38 of themold surface for gelling additional plastisol to a predeterminedthickness over the first area 34 of the mold surface. An oil, such as ahydraulic oil, may be utilized in the fluid or liquid passages 32 and 36as the heat conducting medium. Preferably, the liquid used is made byDow Chemical under the trademark "DOWTHERM A" and comprises 26.5%diphenyl [C₆ H₅ C₆ H₅ ] and 73.5% diphenyl oxide [(C₆ H₅)₂ O]. When themold 16 is first filled with plastisol, the solenoid-actuated controlvalves V₁, V₂, V₃ and V₄ are closed and the valves V₅, V₆, V₇ and V₈ areopen and oil is circulated through both manifolds 40 and 46 by the pumpP₂ and the oil is heated by the heater I which is a gas burning heatexchanger. A thermo couple or thermistor is associated with the moldsurface of the mold 16 and when the mold surface reaches approximately150° all of the valves are closed and the mold support means 14 isrotated to dump or empty the mold 16 into the dump tank 30. When thefirst and second areas 34 and 38 of the mold surface are heated to arange of approximately 130° F. to 150° F. a thin coating is applied overthe mold surface. This coating or layer is actually applied as the mold16 is filled and emptied of plastisol, as some of the liquid plastisolcovers the mold surface or flows into the intricacies thereof during theemptying motion. After the mold is emptied, it is returned to theupright position. A limit switch is associated with the mold supportmeans to provide a signal when the mold support means is returned to theupright position illustrated in FIG. 1. When the mold support meansreturns to the upright position, only the solenoid-actuated valves V₆and V₇ are open to supply hot oil through the manifold 40 and to theliquid passages 32 for heating the first areas 34 of the mold surface.The oil is approximately 400° F. and heats the first areas 34 of themold surface to a range of 250° F. to 260° F. as the mold is refilled oradditional plastisol placed in the mold for gelling the plastisol in thefirst areas 34 of the mold surface. During this period the temperatureof the mold surface in the second areas is maintained at a non-gellingtemperature. Another thermocouple provides a signal when the moldsurface temperature is approximately 250° F. to provide a signal forpouring the additional plastisol into the mold 16. It will beappreciated by those skilled in the art that the temperature of thefirst areas may be raised for gelling before or during or after thefilling of the mold depending upon the design of the mold and otherfactors. A timer may be provided to provide a predetermined time theplastisol is subjected to the 250° temperature of the mold for providinga predetermined thickness in the article before the mold support means14 is again rotated for emptying the additional plastisol into the dumptank 30. When the mold support means 14 is rotated back to the uprightposition, valves V₅, V₆, V₇ and V₈ are opened to supply the 450° oilthrough both liquid passages 32 and 36 so the mold surface temperaturein all areas reaches a range of 350° F. to 400° F. for gelling theplastisol over the second areas and curing or fusing the entire finishedplastisol article over both the first and second areas. After thecuring, the mold support means rotates to a position where the moldfaces outwardly or is in a generally perpendicular position and valvesV₅, V₆, V₇ and V₈ are closed and valves V₁, V₂, V₃ and V₄ are opened tosupply cool oil through liquid passages 32 and 36 for cooling the moldsurface whereby the article may be manually stripped from the mold. Thiscooling brings the mold temperature down to approximately 150°, atemperature desired for the first filling of the mold in making the nextarticle. The oil flow in the cooling circuit passes through the coolerand pump P₁ and is preferably at a temperature of approximately 80° F.An appropriate electrical control circuit actuates the valves and thedrive mechanism for rotating the mold support means in the propersequence. Alternatively, the thermocouples and other controls mayprovide signals to an operator who may, in turn, manually actuate eachsuccessive sequence.

The modular unit 26 includes a framed structure of structural beamssupported on the rollers 28. As alluded to above, the frame structuresupports two complete plastisol supply systems or modules, only one ofwhich will be described in conjunction with FIGS. 1 and 4. The framestructure supports a plastisol storage tank 56 and a plastisol heatexchanger 58. The plastisol heat exchanger 58 has a heating coil passingtherethrough through which hot liquid may be passed for heating theplastisol to maintain its proper viscosity.

There is also included a pump 60 for circulating the plastisol throughthe system.

There is also included a supply conduit means 62 for supplying plastisolto the mold 16. The conduit 62 has a swivel 64 therein so the end of theconduit 62 may be moved upwardly and out of the way by an actuator 66.The flow of plastisol to the mold 16 is controlled by a valve 68. Thebottom of the plastisol tank 56 has a conduit leading to the valve 68and teed off that conduit is a line 70 which extends to a valve 72adjacent the top of the heat exchanger 58. A drain line 74 leads fromthe bottom of the dump tank 30 into the pump 60 to the heat exchanger58. Another conduit 76 extends from the dump tank 30 upwardly to a valve78 with a conduit 80 connected thereto and to a valve 82. In certainmodes of operation the valves 72 and 82 will be closed and the valve 78will be open whereby liquid plastisol will be circulated from the drainline 74 through the pump 60, heat exchanger 58, the valve 78 and backthrough the line 76 into the dump tank for circulation and heatingthereof. Alternatively, the valve 78 and the valve 82 may be closedwhereby liquid plastisol moves from the dump tank through the pump 60,the heat exchanger 58, the valve 72, line 70 and to the plastisol tank56 or through the valve 68 to be dumped from the conduit 62 into themold 16. The conduits 74 and 76 define return conduit means forreturning the plastisol from the dump tank 30 to the storage tank 56. Asexplained hereinbefore, when the mold support means 14 is rotated,plastisol in the mold 16 is dumped into the dump tank 30.

The modular unit includes another independent plastisol supply andretrieval means or module with its circuit heating, storing, etc.,components, and is generally shown at 84 in FIG. 1. The module or system84 is identical to the module having the components describedimmediately above. The advantage of having two independent modules orsystems on one modular unit is that two different plastisols may beutilized for the initial layer or coating as distinguished from thesubsequent gelling of an additional thickness in the article. Further,with one modular unit, an article of two different plastisols or aplastisol of two different colors may be made in short consecutive runs.Because two different plastisols may be utilized, the top of the dumptank 30 includes channels 86 at either end into which rollers areslidably disposed. The rollers are attached to a cover plate which isactuated by a pulley cable system 88. Another dump tank which is notshown is disposed immediately rearwardly of the dump tank 30 and when asecond plastisol is utilized which is incompatible with the plastisol inthe tank 30, the plate is moved by the cable pulley system 88 to aposition to cover the dump tank 30 so that when the mold is emptied, theplastisol will flow over the cover plate rearwardly and downwardly andinto the secondary dump tank disposed rearwardly of the dump tank 30.Additionally, another complete modular unit including one or moremodules may be moved into position for making articles of additionaldifferent plastisols.

Thus, the control means includes a hot liquid circuit having controlvalves, a pump P₂, a first heat exchange means, comprising the heater I,for sequentially supplying liquid to the first and second supply lines48 and 50 and a cold liquid circuit having control valves, a pump P₁ anda second heat exchange means, comprising the cooler, for sequentiallysupplying liquid to the first and second supply lines 48 and 50.

OPERATION OF PREFERRED EMBODIMENT

Thus, in accordance with the subject invention, initially all of thepassages 32 and 36 are supplied with liquid oil to heat or cool thefirst and second areas 34 and 38 of the mold surface to maintain anon-gelling temperature and a liquid plastisol is poured into the moldto define a coating or layer. To accomplish this, the mold is filled andemptied into the dump tank 30. As mentioned above, the liquid coating isapplied to avoid surface defects in the finished product. Depending uponthe mold configuration it may not always be necessary to perform thisliquid coating step. In other words, in some cases it may be possible tofirst gel the plastisol over the first areas while maintaining theplastisol over the second areas in a non-gelled condition. After thecoating is applied, the first group of passages 32 are supplied with aliquid oil at a temperature higher than the temperature of the liquidoil in the second group of passages 36 for heating the first area 34 toa higher temperature than the second area 38. Additional liquidplastisol is disposed over the coating or layer and gelled over thefirst area 34 of the mold which is heated with the heat supplied by theliquid in the first group of passages 32 to gel a predeterminedthickness of the article over the first area 32. The temperature of theliquid in the second group of passages 36 is maintained and arranged toprevent any appreciable gelling of liquid plastisol over the area 38 ofthe mold heated by the second group of passages 36 to prevent thebuild-up of gelled plastisol in those areas of the finished articlewhere the additional thickness is not necessarily required and is oftenwasteful. As mentioned above, the temperature of the first area may beraised to a gelling temperature before or during or after the mold isfilled with plastisol. After the mold 16 is emptied the second time whenthe plastisol has gelled in the first area 34 to the desired thickness,both the first and second groups of passages 32 and 36 are supplied withheated liquid to heat the first and second areas 34 and 38 for gellingthe plastisol in the second area and curing and fusing the plastisolover both the first and second areas. Although the steps of the methodare distinct, they may be preformed sequentially or simultaneously. Inother words, heating and/or cooling of the mold may be accomplished asthe plastisol is added or dumped.

As will be appreciated, by preventing the build-up of the thickness ofthe finished article in the areas of the finished article which may betrimmed or which may not be used, a great deal of plastisol may bereused and recirculated and therefore does not end up in the finishedarticle, thereby providing a significant savings in material costs.Further, because of the method and system employed, the plastisol is notsubjected to any open flame heat, as the heat is supplied in a closedcircuit and, in a similar fashion, the mold may be cooled by a closedsystem instead of being subjected to sprayed water, or the like.

An example of an article which may be made in accordance with thesubject invention is disclosed in the abovementioned U.S. Pat. No.3,315,016 and the information set forth in that patent relative to andin regard to making that article are incorporated herein by thisreference.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method for molding aplurality of articles of heat-fusing material and of different colors inan open shell mold, said method comprising the steps of: supporting anopen shell mold for rotation about an axis to empty the mold of liquidheat-fusing material, positioning a first module in position relative tothe mold for supplying a first color of heat-fusing material to the moldand for receiving the liquid material emptied from the mold to mold aplurality of articles of a first color which are sequentially removedfrom the mold, moving the first module and its first color contents awayfrom the mold and positioning a second module in position relative tothe mold for supplying a second color of different from said first colorheat-fusing material to the mold and for receiving the liquid materialemptied from the mold to mold a plurality of articles of a second colorwhich are sequentially removed from the mold.